Alumina layer with multitexture components

ABSTRACT

A cutting tool insert for machining by chip removal includes a body of a hard alloy of cemented carbide, cermet, ceramics or cubic boron nitride based material onto which a hard and wear resistant coating is deposited by CVD. The coating includes at least one multitextured α-Al 2 O 3  layer with a thickness between 0.5 μm and 30 μm characterized with an ODF texture index&gt;1 and at least two dominant texture components with 2&lt;ODF density&lt;100 coexisting within the layer. A method of making and using the cutting tool insert are also described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coated cutting tool comprising a bodycoated combining a multi textured alpha-alumina (α-Al₂O₃) layer, themethod of making and use the same. The layer is grown by chemical vapourdeposition (CVD) and the invention provides an oxide layer with improvedwear properties and good chip forming machining properties.

2. Description of the Related Art

Typically, CVD alumina based coatings comprise an inner layer oftitanium carbonitride and an outer layer of Al₂O₃. The development anduse comprise different Al₂O₃ polymorphs, e.g., α-Al₂O₃, κ-Al₂O₃ andγ-Al₂O₃ as well as multilayer structures thereof.

U.S. Pat. No. 3,967,035 discloses an α-Al₂O₃ coated cutting tool insertwhere the layer is bonded to the insert through a thin intermediatelayer of an iron group metal aluminate.

U.S. Pat. No. 3,836,392 discloses an α-Al₂O₃ coated cutting tool insertwhere the layer is deposited directly onto the insert.

U.S. Pat. No. 3,837,896 discloses an α-Al₂O₃ coated cutting tool insertwhere an intermediate carbide or nitride layer is deposited prior to theoxide layer.

U.S. Pat. No. 4,619,866 discloses an α-Al₂O₃ coated cutting tool insertwhere the oxide is deposited utilizing a dopant selected from the groupconsisting of sulphur, selenium, tellurium, phosphorous, arsenic,antimony, bismuth and mixtures thereof, dramatically increasing thegrowth rate of the layer.

U.S. Pat. No. 5,968,595 discloses a cutting tool insert coated withsingle- or multilayers, comprising at least one layer of a {210}textured κ-Al₂O₃.

U.S. Pat. No. 5,162,147 discloses a cutting tool insert coated with aninner α-Al₂O₃ layer and an outer κ-Al₂O₃ layer.

U.S. Pat. No. 5,700,569 discloses a multilayer oxide coated cutting toolinsert comprising layers of either α-Al₂O₃ or κ-Al₂O₃.

U.S. Pat. No. 6,015,614 discloses a cutting tool insert coated with amultilayer structure of TiN/TiC on a thick layer of a single and/orbi-layer of α-Al₂O₃ and κ-Al₂O₃.

U.S. Pat. No. 6,632,514 discloses a cutting tool insert coated with amultilayer of κ-Al₂O₃ and TiN or Ti(C,N) layers.

U.S. Pat. No. 7,470,296 discloses a cutting tool insert coated with amultilayer comprising layers of Ti(C,N) and Al₂O₃, preferably κ-Al₂O₃.

U.S. Pat. No. 6,855,413 discloses a cutting tool insert coatedmultilayer comprising layers of TiN and κ-Al₂O₃.

U.S. Pat. No. 6,572,991 discloses an oxide coated cutting tool insertwith an outer layer a layer of γ-Al₂O₃.

U.S. Pat. No. 6,689,450 discloses a coated cutting tool insert having amultilayer of κ-Al₂O₃ and or γ-Al₂O₃ or TiN.

Further enhancement of the oxide layers has recently been achievedthrough the control of crystallographic orientation, texture, especiallyfor the α-Al₂O₃ polymorph. This has been achieved by the development ofnew synthesis routes comprising the use of nucleation and growthsequences, bonding layers, sequencing of the reactant gases, addition oftexture modifying agents and/or by using alumina conversion layers.Commonly, the texture is evaluated by the use of X-ray diffraction (XRD)techniques and the concept of texture coefficients.

Textured Alumina Layer Synthesis Using Various Bonding/Nucleation Layersand Growth Sequences

U.S. Pat. No. 7,094,447 discloses a method to produce textured α-Al₂O₃layers with improved wear resistance and toughness. The α-Al₂O₃ layer isformed on a (Ti,Al)(C,O,N) bonding layer using a nucleation sequencecomposed of aluminizing and oxidization steps. The layer ischaracterized by a {012} growth texture as determined by XRD.

U.S. Pat. No. 7,442,431 discloses a method to produce textured α-Al₂O₃layers on a (Ti,Al)(C,O,N) bonding layer using a nucleation sequencecomposed of short pulses and purges of Ti-containing pulses andoxidizing pulses. The layer is characterized by a {110} growth textureas determined by XRD.

U.S. Pat. No. 7,455,900 discloses a method to produce textured α-Al₂O₃layers on a (Ti,Al)(C,O,N) bonding layer using a nucleation sequencecomposed of short pulses and purges consisting of Ti+Al pulses andoxidizing pulses. The layer is characterized by a {116} growth textureas determined by XRD.

U.S. Pat. No. 7,442,432 discloses a method to produce textured α-Al₂O₃layers on a (Ti,Al)(C,O,N) bonding layer with a modified but similartechnique as disclosed in U.S. Pat. No. 7,455,900. The layer ischaracterized by a {104} growth texture as determined by XRD.

US 2007104945 discloses a textured α-Al₂O₃ coated cutting tool insertfor which a nucleation controlled α-Al₂O₃ layer texture is obtained. Thelayer is characterized by a {006} growth texture as determined by XRD.

US 2008187774 discloses a texture-hardened α-Al₂O₃ coated cutting toolinsert with a {006} growth texture as determined by XRD.

U.S. Pat. No. 6,333,103 discloses a textured α-Al₂O₃ layer grown on aTi(C,O) bonding layer characterized by a {10(10)} growth texture asdetermined by XRD.

Textured Alumina Layer Synthesis Using Sequencing of Reactant Gases

U.S. Pat. No. 5,654,035 discloses a body coated with refractory single-or multilayers, wherein specific layers are characterized by acontrolled microstructure and phase composition with crystal planesgrown in a preferential direction with respect to the surface of thecoated body (growth texture). The textured α-Al₂O₃ layer is obtained bysequencing of the reactant gases in the following order: CO₂, CO andAlCl₃. The layer is characterized by a {012} growth texture asdetermined by XRD.

U.S. Pat. No. 5,766,782 discloses a cutting tool coated with refractorysingle- or multilayers including α-Al₂O₃, wherein specific layers arecharacterized by a controlled growth texture with respect to the surfaceof the coated body. The textured α-Al₂O₃ layer is obtained by sequencingof the reactant gases such that first CO₂ and CO are supplied to thereactor in an N₂ and/or Ar atmosphere followed by supplying H₂ and AlCl₃to the reactor. The layer is characterized by a {104} growth texture asdetermined by XRD.

Textured Alumina Layer Synthesis Using Texture Modifying Agents

U.S. Pat. No. 7,011,867 discloses a coated cutting tool comprising oneor more layers of refractory compounds out of which at least one layeris an α-Al₂O₃ layer having a columnar grain-structure and a {300} growthtexture as determined by XRD. The microstructure and texture is obtainedby adding ZrCl₄ as a texture modifying agent to the reaction gas duringgrowth.

U.S. Pat. No. 5,980,988 discloses a {110} textured α-Al₂O₃ layer asobtained by using SF₆ as a texture modifying agent during growth. Thetexture is determined by XRD.

U.S. Pat. No. 5,702,808 discloses a {110} textured α-Al₂O₃ layer asobtained sequencing SF₆ and H₂S during growth. The texture is determinedby XRD.

Textured Alumina Layer Synthesis Using Conversion Layers

US RE41111 discloses a {0001} textured α-Al₂O₃ layer as obtained usingan initial heat treated alumina core layer (conversion layer) with athickness of 20-200 nm. The texture is determined by electron backscattering diffraction (EBSD).

An explanation of EBSD and the analysis for texture evaluation by usingpole figures, pole plots, orientation distribution functions (ODFs) andtexture indexes can for instance be found in Introduction to TextureAnalysis: Macrotexture, Microtexture, and Orientation Mapping, ValerieRandle and Olaf Engler, (ISBN 90-5699-224-4) pp. 13-40.

SUMMARY OF THE INVENTION

Typically, the evaluation of texture may comprise

-   -   i) construction of the ODF,    -   ii) identifying the components Euler angles φ₁, Φ and φ₂ (cf.        FIG. 5) and their corresponding ODF densities and        crystallographic indices,    -   iii) construction of pole figure(s) of relevant texture        components, and/or    -   iv) construction of pole plot(s) of the relevant texture        components.

It is an object of the present invention to provide a multitexturecontrolled α-Al₂O₃ layer deposited by CVD with improved wear propertiesand chip forming cutting performance.

It is also an object of the present invention to provide a method ofproducing the same.

Surprisingly, it has been found that the control of a multitexturedα-Al₂O₃ layer is obtained solely by the growth conditions resulting intailorable α-Al₂O₃ layers with improved metal cutting properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Examples of the deposition of α-Al₂O₃ varying between theprocess conditions A, B, etc. periodically/aperiodically,upwards/downwards and/or continuously/stepwise.

FIG. 2. SEM micrographs of fractured cross sections of (a) amultitextured {01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃ layer (II) andTi(C,N) layer (I) according to the invention and (b) a single textured{0001} α-Al₂O₃ layer (II) and Ti(C,N) layer (I) according to prior art.

FIG. 3. X-ray diffraction (XRD) pattern from a multitextured{01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃ layer according to theinvention.

FIG. 4. Back scattered SEM micrographs of polished plan views of (a) amultitextured {01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃ layer according tothe invention and (b) a single textured {0001} α-Al₂O₃ layer accordingto prior art.

FIG. 5. Definition of the Euler angles φ₁, Φ, and φ₂ used in the ODFrepresentation with respect to the crystallographic orientations.

FIG. 6. ODF contouring charts (Euler angles and densities) of (a) amultitextured {01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃ layer, denoted asA, A′, B and B′ respectively, according to the invention with its{01-15}, {10-15}, {01-12}, and {10-12} solutions and (b) a singletextured {0001} α-Al₂O₃ layer according to prior art.

FIG. 7. EBSD pole figures of (a) {01-12}, {01-15}, {10-12}, and {10-15}texture components and (b) {0001} textured α-Al₂O₃ layer according toprior art.

FIG. 8. EBSD pole plots of (a) {01-15} texture component, (b) {10-15}texture component, (c) {01-12} texture component, (d) {10-12} texturecomponent of a multitextured {01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃layer and (e) a single textured {0001} α-Al₂O₃ layer according to priorart. χ is the angle from the centre (χ=0) to the rim (χ=90) of the polefigures (cf. FIG. 7). MUD is the multiples of unit distribution.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, there is provided a cutting toolinsert for machining by chip removal comprising a body of a hard alloyof cemented carbide, cermet, ceramic, cubic boron nitride based materialonto which a hard and wear resistant coating is deposited by CVDcomprising at least one α-Al₂O₃ layer, herein defined as a multitexturedα-Al₂O₃ layer, with

-   -   an ODF texture index>1, preferably 1<ODF texture index<50, most        preferably 1<ODF texture index<10, and    -   at least two dominant texture components, i.e., the highest ODF        densities, each of which having 2<ODF density<100, preferably        2<ODF density<50, most preferably 3<ODF density<25, coexisting        within the layer.

Preferably said multitextured α-Al₂O₃ layer has a rotational symmetry,fibre texture, relative to the surface normal of the coated body.

The texture is evaluated using pole figures, pole plots, orientationdistribution functions (ODFs) and texture indexes from, e.g., EBSD orXRD data.

Said multitextured α-Al₂O₃ layer has a thickness between 0.5 μm and 30μm, preferably between 0.5 μm and 20 μm, most preferably between 1 μmand 10 μm, with a columnar grain structure with an average column widthbetween 0.1 μm and 5 μm, preferably between 0.1 μm and 2.5 μm and anuntreated (as-deposited) surface roughness of Ra<1.0 μm over a length of10 μm, preferably between 0.2 μm and 0.5 μm using a stylus profilometer.The column width is determined from back scattered SEM micrographs ofpolished plan views (top surface of the coating) and evaluated using,e.g., the EBSD Channel 5 program package.

In one preferred embodiment, said texture components have the highestODF densities for {01-15}, {10-15}, {01-12}, and {10-12} satisfying oneor both of the {01-15} or {10-15} solutions and one or both of {01-12}or {10-12} solutions with Euler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{10-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 61°<φ₂<119°,preferably 70°<φ₂<110°, and/orand{01-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 12°<φ₂<48°,preferably 24°<φ₂<36°, and/or{10-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 72°<φ₂<108°,preferably 78°<φ₂<102°, and/or

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, and {0001} satisfying one orboth of the{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 61°<φ₂<119°,preferably 70°<φ₂<110°, and/orand{0001}: 0°≦φ₁≦90°, 0°≦Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ_(2≦)120°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, and {10-10} satisfying oneor both of the {01-15} or {10-15} solutions and the {10-10} solutionwith Euler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{10-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 61°<φ₂<119°,preferably 70°<φ₂<110°, and/orand{10-10}:0°≦φ₁≦90°, 75°<Φ<90°, preferably 80°<Φ<90°, and 15°<φ₂<45°,preferably 20°<φ₂<40°, and 75°<φ₂<105°, preferably 80°<φ₂100°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, {11-20}, and {−1-120}satisfying one or both of the {01-15} or {10-15} solutions and one orboth of {11-20} or {−1-120} solutions with Euler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{10-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 61°<φ₂<119°,preferably 70°<φ₂<110°, and/orand{11-20}:0°≦φ₁≦90°, 75°<Φ<90°, preferably 80°<Φ≦90°, and 45°<φ₂<75°,preferably 50°<φ₂<70°, and/or{1-120}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 105°<φ₂≦120°,preferably 110°<φ₂≦120°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-12}, {10-12} and {0001} satisfying one orboth of the {01-12} or {10-12} solutions and the {0001} solution withEuler angles:{01-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 12°<φ₂<48°,preferably 24°<φ₂<36°, and/or{10-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 72°<φ₂<108°,preferably 78°<φ₂<102°, and/orand{0001}: 0°≦φ₁≦90°, 0°≦Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ₂≦120°.

In another preferred embodiment, said texture components have thehighest ODF densities for {0001}, {11-20}, and {−1-120} satisfying the{0001} solution and one or both of the {11-20} or {−1-120} solutionswith Euler angles:{0001}: 0°≦φ₁≦90°,0°≦Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ₂≦120°,and{11-20}: 0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 45°<φ₂<75°,preferably 50°<φ₂<70°, and/or{−1-120}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 105°<φ₂≦120°,preferably 110°<φ₂≦120°, and/or

In another preferred embodiment, said texture components have thehighest ODF densities for {0001} and {10-10} satisfying the {0001}solution and the {10-10} solution with Euler angles:{0001}: 0°≦φ₁≦90°, 0°≦Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ₂≦120°,and{10-10}: 0°≦φ₁≦90°, 75°<Φ<90°, preferably 80°<Φ<90°, and 15°<φ₂<45°,preferably 20°<φ₂<40°, and 75°<φ₂<105°, preferably 80°<φ₂100°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-12}, {10-12}, {11-20}, and {−1-120}satisfying one or both of the {01-12} or {10-12} solutions and one orboth of the {11-20} or {1-1-120} solutions with Euler angles:{01-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 12°<φ₂<48°,preferably 24°<φ₂<36°, and/or{10-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 72°<φ₂<108°,preferably 78°<φ₂<102°, and/orand{11-20}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 45°<φ₂<75°,preferably 50°<φ₂<70°, and/or{−1-120}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 105°<φ₂≦120°,preferably 110°<φ₂≦120°, and/or

In another preferred embodiment, said texture components have thehighest ODF densities for {01-12}, {10-12}, and {10-10} satisfying oneor both of the {01-12} or {10-12} solutions and the {10-10} solutionwith Euler angles:{01-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 12°<φ₂<48°,preferably 24°<φ₂<36°, and/or{10-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 72°<φ₂<108°,preferably 78°<φ₂<102°, and/orand{10-10}:0°≦φ₁≦90°, 75°<Φ<90°, preferably 80°<Φ<90°, and 15°<φ₂<45°,preferably 20°<φ₂<75°, and/or

In another preferred embodiment, said texture components have thehighest ODF densities for {10-10}, {11-20}, and {−1-120} satisfying the{10-10} solution and one or both of the {11-20} or {−1-120} solutionswith Euler angles:{10-10}:0°≦φ₁≦90°, 17°<Φ<90°, preferably 80°<Φ<90°, and 15°<φ₂<45°,preferably 80°<φ₂<100°,and{11-20}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 45°<φ₂<75°,preferably 50°<φ₂<70°, and/or{−1-120}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 105°<φ₂≦120°,preferably 110°<φ₂≦120°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, {0001}, and {10-10}satisfying one or both of the {10-15} or {01-15} solutions and the{0001} solution and the {10-10} solution with Euler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{10-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 61°<φ₂<119°,preferably 70°<φ₂<110°, and/orand{0001}: 0°≦φ₁≦90°, 0°≦Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ₂≦120°,and{10-10}:0°≦φ₁≦90°, 75°<Φ<90°, preferably 80°<Φ<90°, and 15°<φ₂<45°,preferably 20°<φ₂<40°, and 75°<φ₂<105°, preferably 80°φ₂<100°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-12}, {10-12}, {0001}, and {10-10}satisfying one or both of the {01-12} or {10-12} solutions and the{0001} solution and the {10-10} solution with Euler angles:{01-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 12°<φ₂<48°,preferably 24°<φ₂<36°, and/or{10-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 72°<φ₂<108°,preferably 78°<φ₂<102°,and{0001}:0°≦φ₁≦90°, 0°<Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ₂≦120°,and{10-10}:0°≦φ₁≦90°, 75°<Φ<90°, preferably 80°<Φ<90°, and 15°<φ₂<45°,preferably 20°<φ₂<40°, and 75°<φ₂<105°, preferably 80°<φ₂<100°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, {0001}, {11-20}, and{−1-120} satisfying one or both of the {10-15} or {01-15} solutions andthe {0001} solution and one or both of the {11-20} or {−1-120} solutionswith Euler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{10-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 61°<φ₂<119°,preferably 70°<φ₂<110°,and{0001}:0°≦φ₁≦90°, 0°≦Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ₂≦120°,and{11-20}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 45°<φ₂<75°,preferably 50°<φ₂<70°, and/or{−1-120}:0°≦φ₁≦90°, 75°<Φ≦90°, preferably 80°<Φ≦90°, and 105°<φ₂≦120°,preferably 110°<φ₂≦120°.

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, {01-12}, {10-12}, and {0001}satisfying one or both of the {10-15} or {01-15} solutions and one orboth of the {01-12} or {10-12} solutions and the {0001} solution withEuler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/orand{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/orand{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, {10-10}, {01-12}, and{10-12} satisfying one or both of the {10-15} or {01-15} solutions andthe {0001} solution and one or both of the {01-12} or {10-12} solutionswith Euler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/orand{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/orand{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or

In another preferred embodiment, said texture components have thehighest ODF densities for {01-15}, {10-15}, {10-10}, {01-12}, {10-12},and {0001} satisfying one or both of the {10-15} or {01-15} solutionsand {10-10} solution and one or both of the {01-12} or {10-12} solutionsand the {0001} solution with Euler angles:{01-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 1°<φ₂<59°,preferably 10°<φ₂<50°, and/or{10-15}:0°≦φ₁≦90°, 17°<Φ<47°, preferably 22°<Φ<42°, and 61°<φ₂<119°,preferably 70°<φ₂<110°,and{10-10}:0°≦φ₁≦90°, 75°<Φ<90°, preferably 80°<Φ<90°, and 15°<φ₂<45°,preferably 20°<φ₂<40°, and 75°<φ₂<105°,and{01-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 12°<φ₂<48°,preferably 24°<φ₂<36°, and/or{10-12}:0°≦φ₁≦90°, 43°<Φ<73°, preferably 48°<Φ<68°, and 72°<φ₂<108°,preferably 78°<φ₂<102°,and{0001}: 0°≦φ₁≦90°, 0°≦Φ<15°, preferably 0°≦Φ<10°, and 0°≦φ₂≦120°.

Said coating may comprise of an inner single- and/or multilayers of,e.g. TiN, TiC or Ti(C,O,N) or other Al₂O₃ polymorphs, preferablyTi(C,O,N), and/or an outer single- and/or multilayers of, e.g. TiN, TiC,Ti(C,O,N) or other Al₂O₃ polymorphs, preferably TiN and/or Ti(C,O,N), toa total thickness 0.5 to 40 μm, preferably 0.5 to 30 μm, and mostpreferably 1 to 20 μm, according to prior art.

Optionally, said coated body is post treated with, e.g., wet blasting,brushing operation, etc. such that the desired surface quality isobtained.

According to the invention, the deposition method for the multitexturedα-Al₂O₃ layer of the present invention is based on chemical vapourdeposition at a temperature between 950 C and 1050 C in mixed H₂, CO₂,CO, H₂S, HCl and AlCl₃ at a gas pressure between 50 and 150 mbar asknown in the art. During deposition, the CO₂/CO gas flow ratio isperiodically or aperiodically varied, upwards and downwards,continuously or stepwise between at least two gas flow ratios chosenwithin the interval 0.3≦(CO₂/CO)≦6 and with a difference of at least0.1. The time between the starting points for the chosen gas flow ratiosis between 1 and 60 minutes, preferably between 2 and 30 minutes. It iswithin the purview of the skilled artisan to determine the detailedprocess conditions in accordance with the present description.

This invention also relates to the use of cutting tool inserts accordingto the above for machining by chip removal at cutting speeds between 75and 600 m/min, preferably between 150 and 600 m/min, with an averagefeed, per tooth in the case of milling, between 0.08 and 0.5 mm,preferably between 0.1 and 0.4 mm depending on cutting speed and insertgeometry.

Example 1

Cemented carbide inserts with the composition 5.5 wt % Co, 8 wt % cubiccarbides and balance WC, were initially coated with a 6 μm thick layerof MTCVD Ti(C,N). In subsequent process steps and during the samecoating cycle, a 5 μm thick layer of a multitextured α-Al₂O₃ wasdeposited with the general process conditions given in table 1 and thespecific process conditions, indexed with A, B, C and D, given in table2. The α-Al₂O₃ layer was deposited with a periodical and continuouschange between process conditions A, B, C and D, and in time steps setby the process time ratios t_(A): t_(B): t_(c): t_(D) where i=A, B, C,D, is the time between two consecutive process conditions. The periodtime is t_(A)+t_(B)+t_(c)+t_(D).

TABLE 1 General process conditions CO₂ + CO/% 7.5 AlCl₃/% 2 H₂S/% 0.3HCl/% 2 H₂/% Balance Pressure/mbar 70 Temperature/° C. 1000

TABLE 2 Specific process conditions (A, B, C and D) Insert(CO₂/CO)_(A):(CO₂/ # CO)_(B):(CO₂/CO)_(C):(CO₂/CO)_(D)t_(A′):t_(B′):t_(C′):t_(D′) Period time 1 1:2:n.a.:n.a. 1:1:n.a.:n.a 40min 2 1:2:n.a.:n.a. 1:1:n.a.:n.a 20 min 3 1:2:n.a.:n.a. 1:1:n.a.:n.a 10min 4 1:2:n.a.:n.a 1:2:n.a.:n.a 30 min 5 1:2:n.a.:n.a 1:3:n.a.:n.a 40min 6 0.5:1:n.a.:n.a 1:1:n.a.:n.a 20 min 7 0.5:1:n.a.:n.a 1:2:n.a.:n.a30 min 8 0.5:1:n.a.:n.a 1:3:n.a.:n.a 40 min 9 0.5:2:n.a.:n.a1:1:n.a.:n.a 20 min 10 0.5:2:n.a.:n.a 1:2:n.a.:n.a 30 min 110.5:2:n.a.:n.a 1:3:n.a.:n.a 20 min 12 0.5:2:n.a.:n.a 1:3:n.a.:n.a 40 min13 2:5:n.a.:n.a 1:1:n.a.:n.a 20 min 14 2:5:n.a.:n.a 1:2:n.a.:n.a 30 min15 2:5:n.a.:n.a 1:3:n.a.:n.a 40 min 16 0.5:5:n.a.:n.a 1:1:n.a.:n.a 20min 17 0.5:5:n.a.:n.a 1:2:n.a.:n.a 30 min 18 0.5:5:n.a.:n.a 1:3:n.a.:n.a40 min 19 0.5:1:2:n.a. 3:1:2:n.a. 60 min 20 1:2:5:n.a. 3:1:1:n.a. 50 min21 1:2:5:n.a. 3:1:1:n.a. 25 min 22 0.5:1:5:n.a. 2:1:1:n.a. 40 min 230.5:2:5:n.a. 1:1:1:n.a. 30 min 24 0.5:1:2:5 1:1:1:1 40 min

Example 2

Example 1 was repeated with a single textured α-Al₂O₃ layer using aconstant CO₂/CO gas flow ratio of 2.0.

Example 3

α-Al₂O₃ layers from example 1 and 2 were characterized by SEM and EBSDusing a LEO Ultra 55 scanning electron microscope operated at 15 kV andequipped with a HKL Nordlys II EBSD detector. The texture was evaluatedfrom the EBSD data by constructing ODF's with series expansion having aresolution of 32×32×32 points and a Gaussian half width of 5° andL_(max)=34 clustering data of 5° over a representative area of apolished top surface of the α-Al₂O₃ layers. The commercial Channel 5software version 5.0.9.0 was used for data collection and also for dataanalyses: calculations of ODFs, i.e. the Euler angles and densities aswell as texture indexes, pole figures, and pole plots.

FIG. 2 shows back scattered SEM micrographs of polished cross sectionsof the α-Al₂O₃ layers, marked with II in the images, for (a) insert 2 inexample 1 (invention) and (b) example 2 (reference). Both layers exhibita columnar grain to structure. The invention layers show a strongreduction of the surface roughness.

The surface roughness of insert 2 in example 1 was Ra=0.35 μm asmeasured by a stylus profilometer over a length of 10 μm.

FIG. 3 shows X-ray diffraction (XRD) patterns from insert 2 in example 1demonstrating a multitextured {01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃layer.

FIG. 4 shows back scattered SEM micrographs of polished plan views of(a) a multitextured {01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃ layer ofinsert 2 in example 1 and (b) a single textured {0001}α-Al₂O₃ layer ofexample 2. The invention layers show reduced column width, in averagebetween 0.1 μm and 2.5 μm as determined from back scattered SEMmicrographs of polished plan views (top surface of the coating) andevaluated using, e.g., the EBSD Channel 5 program package.

FIG. 6 shows ODF contour charts (ODF Euler angles and densities) asdeduced from the EBSD data of (a) a multitextured{01-15}+{10-15}+{01-12}+{10-12} α-Al₂O₃ layer from insert 2 in example 1(table 2) with the {01-15}, {10-15}, {01-12} and {10-12} solutions andan ODF texture index of 4.06, and (b) of a single textured {0001}α-Al₂O₃layer of example 2 with an ODF texture index of 5.5. The Euler anglesφ₁, Φ and φ₂ for the {01-15}, {10-15}, {01-12} and {10-12} solutions ofthe {01-15}, {10-15}, {01-12}, and {10-12} texture components arecentred (highest ODF density) at about{01-15}:0°≦φ₁≦90°, Φ=32° and φ₂=30°,{10-15}:0°≦φ₁≦90°, Φ=32° and φ₂=90°,{01-12}:0°≦φ₁≦90°, Φ=58° and φ₂=30°, and{10-12}:0°≦φ₁≦90°, Φ=58° and φ₂=90°.

From the Channel 5 software, the ODF density values for the {01-15} and{01-12} texture components were deduced as 17.7 and 6.2, respectively.The results demonstrate a multitextured {01-15}+{01-12} fibre texture.

The texture index and texture components with its corresponding ODFdensities for the inserts in example 1 are shown in table 3.

TABLE 3 Insert Texture # index Dominant texture component/ODF density 13.98 {01-15}/16.5 {01-12}/6.1 2 4.06 {01-15}/17.7 {01-12}/6.2 3 4.22{01-15}/17.3 {01-12}/5.9 4 3.94 {01-15}/10.3 {01-12}/12.4 5 4.14{01-15}/8.2 {01-12}/19.2 6 3.81 {01-15}/12.0 {0001}/4.2 7 2.54{01-15}/6.9 {0001}/6.3 8 4.44 {01-15}/5.1 {0001}/15.2 9 4.91{01-12}/15.9 {0001}/3.1 10 2.79 {01-12}/5.7 {0001}/7.1 11 4.91{01-12}/3.2 {0001}/13.9 12 4.83 {01-12}/3.3 {0001}/14.4 13 5.56{01-12}/19.4 {10-10}/6.0 14 4.67 {01-12}/13.2 {10-10}/21.0 15 5.93{01-12}/7.6 {10-10}/24.0 16 3.25 {0001}/14.0 {10-10}/4.3 17 2.95{0001}/5.9 {10-10}/13.4 18 3.85 {0001}/3.1 {10-10}/14.7 19 2.72{01-15}/9.6 {01-12}/3.5 {0001}/5.2 20 3.48 {01-15}/15.5 {01-12}/5.0{10-10}/7.7 21 3.34 {01-15}/14.9 {01-12}/4.9 {10-10}/7.5 22 2.79{01-15}/10.0 {0001}/5.4 {10-10}/5.0 23 2.36 {0001}/6.6 {01-12}/4.2{10-10}/6.4 24 1.78 {01-15}/5.9 {01-12}/4.7 {0001}/4.5 {10-10}/5.2

In addition, pole figures and pole plots of the fibre textures wereplotted.

FIG. 7 shows pole figures of (a) {01-15}, {10-15}, {01-12}, and {10-12}texture components of insert 2 in example 1 and (b) {0001} texturedα-Al₂O₃ layer of example 2.

FIG. 8 shows pole plots of (a) {01-15} texture component, (b) {10-15}texture component, (c) {01-12} texture component, (d) {10-12} texturecomponent of insert 2 in example 1 and (e) a single textured{0001}α-Al₂O₃ layer of example 2. χ is the angle from the centre (χ=0)to the rim (χ=90) of the pole figures (cf. FIG. 4). MUD is the multiplesof unit distribution.

Example 4

Coated inserts from example 1 and example 2 together with competitorgrades were tested in a continuous turning application at the followingcutting conditions.

Work piece: Cylindrical bar

Material: SS1672

Insert type: CNMG120408

Cutting speed: 300 m/min

Feed: 0.35 mm/rev

Depth of cut: 2.5 mm

Remarks: dry

Life time for crater wear was used as criterion.

TABLE 4 Insert Time/minutes Example1: Insert 1 15 Example1: Insert 2 14Example1: Insert 3 14 Example1: Insert 4   13.5 Example 2 13 CompetitorX 13 Competitor Y Break down Competitor Z 11

Example 5

Coated inserts from example 1 and example 2 together with a competitorgrade were tested in a continuous turning application at the followingcutting conditions.

Work piece: Cylindrical bar

Material: SS2258

Insert type: CNMG120408

Cutting speed: 220 m/min

Feed: 0.35 mm/rev

Depth of cut: 2.5 mm

Remarks: dry

Life time for crater wear was used as criterion.

TABLE 5 Insert Time/minutes Example1: insert 2 12 Example1: insert 12 12Example1: insert 19 13 Example 2 11 Competitor X 10

Example 6

Coated inserts from example 1 and example 2 together with a competitorgrade were tested in a continuous turning application at the followingcutting conditions.

Work piece: Cylindrical bar

Material: SS2348

Insert type: CNMG120408

Cutting speed: 180 m/min

Feed: 0.35 mm/rev

Depth of cut: 2.5 mm

Remarks: dry

Life time for crater wear was used as criterion.

TABLE 6 Insert Time/minutes Example1: insert 1 17 Example1: insert 5 18Example 2 16 Competitor X 16

The invention claimed is:
 1. A cutting tool insert for machining by chipremoval comprising a body of a hard alloy of cemented carbide, cermet,ceramics or cubic boron nitride based material onto which a hard andwear resistant coating is deposited by CVD comprising: at least oneα-Al₂O₃ layer with a thickness between 0.5 μm and 30 μm, having an ODFtexture index>1, and at least two dominant texture components with 2<ODFdensity<100 coexisting within the layer.
 2. The cutting tool insertaccording to claim 1, wherein 1<ODF texture index<50.
 3. The cuttingtool insert according to claim 1, wherein 1<ODF texture index<10.
 4. Thecutting tool insert according to claim 1, wherein 2<ODF density<50. 5.The cutting tool insert according to claim 1, wherein 3<ODF density<25.6. The cutting tool insert according to claim 1, wherein said layer isfibre textured.
 7. The cutting tool insert according to claim 1, whereinsaid layer has a columnar grain structure with an average column widthbetween 0.1 μm and 5 μm.
 8. The cutting tool insert according to claim1, wherein said layer has a surface roughness Ra<1.0 μm.
 9. The cuttingtool insert according to claim 1, wherein said layer comprises texturecomponents with Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₁≦90°, 43°<Φ<73°, and 72°<φ₂<108°.
 10. The cutting tool insertaccording to claim 1, wherein that said layer comprises texturecomponents with Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°,0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°.
 11. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°.
 12. The cuttingtool insert according to claim 1, wherein said layer comprises texturecomponents with Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 75°<Φ≦90°, and 45°<φ₂<75°, and/or 0°≦φ₁≦90°, 75°<Φ≦90°, and105°<φ₂≦120°.
 13. The cutting tool insert according to claim 1, whereinsaid layer comprises texture components with Euler angles0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₁≦90°, 43°<Φ<73°, and 72°<φ₂<108°,and0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°.
 14. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°,and0°≦φ₁≦90°, 75°<Φ≦90°, and 45°<φ₂<75° and/or0°≦φ₁≦90°, 75°<Φ≦90°, and 105°<φ₂≦120°.
 15. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°,and0°≦φ₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°.
 16. The cuttingtool insert according to claim 1, wherein said layer comprises texturecomponents with Euler angles0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₁≦90°, 43°<Φ<73°, and 72°<φ₂<108°and0°≦φ₁≦90°, 75°<Φ≦90°, and 45°<φ₂<75°, and/or0°≦φ₁≦90°, 75°<Φ≦90°, and 105°<φ₂≦120°.
 17. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₁≦90°, 43°<Φ<73°, and 72°<φ₂<108°,and0°≦φ₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°.
 18. The cuttingtool insert according to claim 1, wherein said layer comprises texturecomponents with Euler angles0°≦φ₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°,and0°≦φ₁≦90°, 75°<Φ≦90°, and 45°<φ₂<75°, and/or0°≦φ₁≦90°, 75°<Φ≦90°, and 105°<φ₂≦120°.
 19. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°and0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°,and0°≦φ₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°.
 20. The cuttingtool insert according to claim 1, wherein said layer comprises texturecomponents with Euler angles0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₁≦90°, 43°<Φ<73°, and 72°<φ₂<108°,and0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°,and0°≦φ₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°.
 21. The cuttingtool insert according to claim 1, wherein said layer comprises texturecomponents with Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°,and0°≦φ₁≦90°, 75°<Φ≦90°, and 45°<φ₂<75°, and/or0°≦φ₁≦90°, 75°<Φ≦90°, and 105°<φ₂≦120°.
 22. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₁≦90°, 43°<Φ<73°, and 72°<φ₂<108°,and0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°.
 23. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°,and0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₁≦90°, 43°<Φ<73°, and 72°<φ₂<108°.
 24. The cutting tool insertaccording to claim 1, wherein said layer comprises texture componentswith Euler angles0°≦φ₁≦90°, 17°<Φ<47°, and 1°<φ₂<59°, and/or0°≦φ₁≦90°, 17°<Φ<47°, and 61°<φ₂<119°,and0°≦φ₁≦90°, 0°≦Φ<15°, and 0°≦φ₂≦120°,and0°≦φ₁≦90°, 43°<Φ<73°, and 12°<φ₂<48°, and/or0°≦φ₂≦90°, 43°<Φ<73°, and 72°<φ₂<108°,and0°≦₁≦90°, 75°<Φ<90°, and 15°<φ₂<45°, and 75°<φ₂<105°.
 25. The cuttingtool insert according to claim 1, wherein coating comprises of an innersingle- and/or multilayers of, e.g. TiN, TiC or Ti(C,O,N) or other Al₂O₃polymorphs, and/or an outer single- and/or multilayers of, e.g. TiN,TiC, Ti(C,O,N) or other Al₂O₃ polymorphs to a total thickness 0.5 to 40μm.
 26. A method of making a cutting tool insert comprising a body ofcemented carbide, cermet, ceramics or cubic boron nitride based materialonto which a hard and wear resistant coating comprising at least oneα-Al₂O₃ layer is deposited by chemical vapour deposition at atemperature between 950° C. and 1050° C. in mixed H₂, CO₂, CO, H₂S, HCland AlCl₃ at a gas pressure between 50 and 150 mbar characterised inperiodically varying the CO₂/CO gas flow ratio, upwards and downward,continuously or stepwise between at least two gas flow ratios chosenwithin the interval 0.3≦(CO₂/CO)≦6 and with a difference of at least0.1, wherein, the time between the starting points for the chosen gasflow ratios is between 1 and 60 minutes, preferably between 2 and 30minutes; and wherein, the at least one α-Al₂O₃ layer has a thicknessbetween 0.5 μm and 30 μm, having an ODF texture index>1, and at leasttwo dominant texture components with 2<ODF density<100 coexisting withinthe layer.